Colin McCarthy downs a punt against Seattle. The third-year pro is expected to start at middle linebacker in place of Moise Fokou (knee) for the first time this season against San Francisco.

McCarthy is expected to start at the spot in place of Moise Fokou, who suffered a knee injury against Seattle that will sideline him this Sunday when San Francisco visits Tennessee at 3:05 p.m. (CT).

McCarthy said he “struggled a little bit” in replacing Fokou against the Seahawks, but thinks he will benefit from a full week of preparation as the “Mike” linebacker, where he’s made 14 starts for the Titans during his three-year career.

“I’m excited to get the start this week, get back out there with the guys and get this win before the bye week,” McCarthy said. “It’s an opportunity for me and I’m going to make the most of it, play within the defense, but also make plays. When I was healthy, that’s what I did, and I feel great, so I’m excited to get back out there.”

After demonstrating a knack for creating big plays as a rookie, McCarthy had a frustrating 2012 because of multiple injuries. He suffered a sprained ankle in the opener, which cost him four of the next six games, and missed the final five games because of a concussion.

McCarthy began the offseason as the starter, and the Titans brought in Fokou as the presumptive backup because he had experience as an inside and outside linebacker. When a hamstring sidelined McCarthy this summer, Fokou stepped in and impressed coaches with the way he played and worked with the other defenders.

The Titans have played McCarthy more on special teams this season and he’s responded with 10 tackles on coverage teams.

“He’s accepted his role, which I was happy to see,” Titans coach Mike Munchak said. “He’s made a lot of tackles on special teams, something he really hadn’t done much of in the past.”

Fokou has 45 tackles, which is one shy of the career high he set in Indianapolis last season, and forced two Seahawks fumbles last week.

“I think Moise was really playing well. I really like the way he plays the game. I think that’s contagious, the way that kid plays,” Munchak said. “I think he’s really influence a lot of our players with his work ethic and getting guys lined up and on the same page.”

Munchak said Fokou has done a good job in making quick decisions in response to the multiple offensive looks opponents have presented to the Titans and communicating with the other 10 players before the snap to prepare them for the play.

The Titans believe that the 49ers (4-2) will rely heavily on their powerful rushing attack that they’ve committed to during their three-game winning streak.

“(McCarthy) waited his turn and now here it is and we need him to step up and play well,” Munchak said. “What a game to do it, against San Francisco, that’s going to have six linemen, seven linemen in there, a bunch of three tight ends trapping and whamming it. You’re going to see it all this weekend, so this is a great opportunity for him to step up and help us and we need it. We always thought he’s a very good linebacker and just hasn’t been able to stay healthy. This is a great opportunity.”

McCarthy said his previous experience should help his transition this week.

“I’ve been in this defense for going on three years now, so I think my mindset was just different. I was preparing for punt, getting ready for punt return, and now, I’m ready for defense. I’m excited obviously,” McCarthy said. “Special teams, I’m still going to be part of those, so I’m excited for that, but we need to get this win. We need to get out of this slump and get back to winning games and there’s no better way to go into the bye week than with a win.”

Titans defensive tackle Jurrell Casey, who was drafted one round ahead of McCarthy in 2011, said the familiarity that most defenders have with McCarthy will help.

“You’ve got a guy that’s been there before so he knows the system. It’s not like he comes in and he’s lost,” Casey said. “He knows what’s going on so it’s not a big drop off. He can come in and fill the hole, and that’s one thing we’ve been talking about all year is guys being prepared so when their number is called, they can go out there and show up.”

GREENE PRACTICES: A couple of the passes Locker completed during drills went to Shonn Greene, who has missed the past five weeks with a knee injury he suffered in the season opener.

Offensive coordinator Dowell Loggains said, “He’s still got the hands,” after one of the receptions, and running backs coach Sylvester Croom also kidded Greene after the play. Both are clearly happy to have the powerful running back making strides.

Greene was brought in during free agency because of his experience and style that could complement the speed of Chris Johnson as the Titans wanted to increase their identity and effectiveness as running team.

The Titans want to see how Greene responds to the return of football activities before determining if he’ll be available.

“Shonn Greene’s going to get as many reps as he can during the week,” Munchak said. “We’re going to find out where he’s at and how much he can or can’t play. We’re not going to hold (Greene or Locker) back if they progress at a rapid pace, but we’re not planning on that happening.”

Greene said it’s been tough to be sidelined during short-yardage situations where he excelled with the Jets last season and to not be able to help the Titans in their three close losses.

“I’ve got to go (Thursday) and Friday and see where I am from there,” Greene said. “It’s real frustrating, not only a play here but the whole game, seeing the effort the guys put in and to come up short a couple of times is real frustrating. We’ve just got to keep coming back and working hard and we’ll be alright.”

DILES BACK WITH TITANS: With Fokou and Zaviar Gooden not practicing and with Patrick Bailey limited by a hamstring, the Titans wanted to add depth at linebacker and were able to do so by signing Zac Diles, who played in six games with Tennessee last season before going on injured reserve.

Diles went to Kansas City as a free agent but was released before the season. He had been training in Kansas City when the Titans gave him a call.

The downside of bringing back Diles, a seven-year veteran with 31 starts, was being required to release a player because of limitations on the 53-man roster. The Titans waived receiver Michael Preston but are hoping to bring him back.

“That’s the hard part of having all these linebackers hurt. Mike’s done a great job here, but we lost (Keyunta Dawson) because we had to add the quarterback spot (Rusty Smith as a backup to Ryan Fitzpatrick) a couple of weeks ago, and now (Preston) because of linebackers. The goal is try to get him back here because we think he’s going to develop into a really good player.”

Munchak said Stewart is “a lot better this week” and should be able to practice Thursday and Friday, and coaches opted to rest Pollard’s sore ankle because they thought they might practice indoors because of rain.